A storage area network (SAN) is primarily used to enable a storage device, for example, a disk array, a tape library, and an optical jukebox, accessible to a server, so that the storage device functions like a device that is locally attached to an operating system.
Fibre Channel (FC) was primarily used in the supercomputer field, but has become a standard connection type for a storage area network in enterprise storage. A fibre channel host bus adapter (HBA) is located on a server or a storage device and provides a fibre channel port. Each HBA has a unique world wide name (WWN), which is similar to a media access control (MAC) address in an Ethernet. However, a WWN is longer. There are two types of WWNs on an HBA: a node WWN: a world wide node name (WWNN), which may be shared by some or all ports of a device; and a port WWN: a world wide port name (WWPN), which is unique to each port.
The following types of ports are defined by Fibre Channel: an N_port, that is, an N port, which is a port that is on a node (for example, a host, a server, or a storage device) and that is connected to an FC switched fabric (FC-SW or fabric), and is also referred to as a node port; an F_port, that is, an F port, which is a port on a fibre channel switch that is connected to a node (that is, connected to the N_port), and is also referred to as a fabric port; and an E_port, that is, an E port, which is a connection between two fibre channel switches, and is also referred to as an expansion port.
Node port virtualization (also referred to as N_port virtualization) reduces a quantity of fibre channel domain identifiers (FC domain identifier (ID)) in an SAN. One or more unique domain IDs are specified for each switch in a switched fabric. Usually, a quantity of domain IDs is a quantity of switches in the switched fabric. A switch operating in the node port virtualization (NPV) mode, hereinafter referred to as a node port virtualization switch or an NPV switch for short, does not join a switched fabric that is accessed by the switch, but the switch joins another switched fabric. The NPV switch simulates a port, connected to the switched fabric that is accessed by the NPV switch, as an N_port, and uses an N_port of a node of a switched fabric in which the NPV switch is located as a virtual N_port (VN_port) of the simulated N_port.
In a situation in which an NPV switch is connected to a fibre channel switched fabric by using two or more N ports, for example, in a scenario in which the NPV switch accesses another switched fabric in a load-sharing manner, a node connected to the NPV switch can only be virtualized as a VN_port on one of the N ports. Nodes that are virtualized as VN_ports on different N ports of a same NPV switch cannot communicate with a same remote node at the same time. The remote node refers to a node connected to the switched fabric that is accessed by the NPV switch.